Download chapter 4 - Elkhorn Valley Schools

 Atomic

Theories
A timeline…
or as you may prefer to
remember it…
I believe atoms are the
smallest pieces of matter.
 He
came up with the term “atom”
 He thought atoms had different shapes and
sizes
 He thought they were indivisible and
indestructible
 “atomists” – people who followed his beliefs
 His
beliefs were more like
the early Greeks
 Philosopher
Atoms? Give me a
break! I could
speak for hours
against their
existence.
 Dalton’s




Atomic Theory
Matter is composed of atoms
All atoms of the same element are identical;
different elements have unique atoms
They cannot be destroyed or created
They combine to form compounds
 Discovered
the electron
 Proved the atom can be divided
 Plum pudding model
 Atoms
have a dense “nucleus”
 Discovered the proton
 Discovered
the neutron
 The
number of protons in an atom
 Usually the number of electrons also
 The
number of protons and neutrons
 The “rounded” number
 Neutrons = mass number – atomic number
 Isotopes – atoms possessing the same number
of protons but different neutrons
 The
“unrounded” number
 It’s an average “mass” of all the atoms of an
element in nature